Update UsingAssetBundle.md

增加ab.Unload调用

Design/UsingAssetBundle.md

@@ -40,7 +40,10 @@ public static void Build()
   else
   {
       AssetBundle ab = (request.downloadHandler as DownloadHandlerAssetBundle).assetBundle;
+      // ab.LoadAsset
+      ab.Unload(false);
   }
+  request.Dispose();
   ```
 - UnityWebRequest
   ```c#
@@ -54,7 +57,10 @@ public static void Build()
   } else
   {
       AssetBundle ab = handler.assetBundle
+      // ab.LoadAsset
+      ab.Unload(false);
   }
+  www.Dispose();
   ```
 - WWW.LoadFromCacheOrDownload
   ```c#
@@ -66,6 +72,9 @@ public static void Build()
       yield break;
   }
   AssetBundle ab = www.assetBundle;
+  // ab.LoadAsset
+  ab.Unload(false);
+  www.Dispose();
   ```
 - WWW
   ```c#
@@ -77,6 +86,8 @@ public static void Build()
       yield break;
   }
   AssetBundle ab = www.assetBundle;
+  ab.Unload(false);
+  www.Dispose();
   ```
 
   界面如下
@@ -129,4 +140,4 @@ StartCoroutine(UnityWebRequestLoad(string.Format("http://127.0.0.1:8080/Streamin
 3. Understanding Memory in Unity WebGL
   https://blog.unity.com/technology/understanding-memory-in-unity-webgl
 4. AssetBundle API
-  https://docs.unity3d.com/2019.4/Documentation/ScriptReference/AssetBundle.html
+  https://docs.unity3d.com/2019.4/Documentation/ScriptReference/AssetBundle.html
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